1. Field of the Invention
This invention relates to process and apparatus for preheating fuel for a turbine engine during a generator, and more particularly to extracting heat from lubricating oil for the bearing of the turbine and the generator and applying that heat to relatively cool incoming fuel for the turbine to preheat the fuel.
2. Background of the Invention
In recent years, pipeline natural gas fuel prices have continued to increase dramatically forcing heavy duty combustion turbine power plants to explore cost effective methods for combating rising fuel cost. As the need for higher thermal efficiency in power plants increases, a growing number of combined-cycle power plants are incorporating gas fuel heating as a means for improving overall efficiency. A gas fuel heater can be used to preheat fuel prior to combustion in a gas turbine. Gas fuel heating can reduce the amount of fuel required for achieving a specific firing temperature and thereby improves heat rate.
Gas fuel pre-heating is also required from a dew point consideration. A superheat requirement is determined to ensure that gas is free of liquids and particularly, hydrocarbon droplets, during gas fuel operation. The superheat is a temperature difference between the supply and respective dew point temperature of the gas fuel. Dew point heaters are used to add the desired amount of superheat. Simple cycle power plants typically employ gas fired, oil-fired or electric heaters for fuel heating and combined cycle power plants can use feed water extracted from the heat recovery steam generator (HRSG) at an optimum location.
In existing turbine power plants, heat is generated in the seal oil, turbine turning gear, gas turbine bearings, generator bearings and in the generator cooling water. Currently, the waste heat from gas turbine lubrication, generator and auxiliary system is rejected to the atmosphere via the plant auxiliary cooling water. There is a need to capture some of this waste heat for heating turbine fuel. This waste heat extraction will increase efficiency, reduce heat losses, increase fuel utilization, and lower operating costs for the combustion turbine power plants.